Structural design optimization of knee replacement implants for Additive Manufacturing

Recent developments in additive manufacturing (AM) have led the way to extraordinary opportunities in the development and fabrication of surgical implants due to advantages that AM offers. The study of structural design optimization (SDO) involves strategies such as topology optimization (TO), shape optimization, and size optimization to achieve a desired functionality for a given set of loads and constraints while optimizing specific qualities such as the structure weight or uniform stress distribution. Thus, integration of structural design optimization (SDO) and additive manufacturing (AM) is a powerful way for designing and fabricating lightweight medical implants that replicate the biomechanical properties of the host bones, and minimize stress shielding related problems. This study is focused in proposing a setup of a proper methodology for the rapid development of optimized surgical implants. A tibia intramedullary implant for an 8-year old osteosarcoma patient is designed and optimized, through TO in Abaqus/Tosca, to reduce the weight of the implant and minimize stress shielding related problems. A weight reduction of about 30 % was achieved from structural design optimization. The overall viability of the proposed design concept was validated using finite element analysis (FEA), and a stainless steel 316 L prototype was fabricated via SLM. After analysing results, in order to address osseointegration it is proposed that lattice structures to be incorporated in future work. In addition to that, there will be structural modifications for the implant to be able to adjust as the patient grows. (C) 2019 The Authors. Published by Elsevier B.V.